Electrophoresis is a method for the analysis of proteins in body fluids and has proven to be very valuable in laboratory and clinical work. There have been a number of commercial instruments produced for relatively low resolution applications, in which the electrophoretic medium is a microporous plastic membrane or a polyacrylamide gel which permits resolution of perhaps five components in the material being analyzed. Much higher resolution and accordingly analysis of as many as fifteen components may be obtained utilizing a relatively large area of agarose gel slide which is subjected to electrophoresis under specified controlled condition. Such a slide is formed of an agarose gel with a barbital buffer added. While measurements performed with these slides have shown excellent results in laboratory environments, in order to attain wide spread clinical use, an apparatus for providing easy, economical and particularly accurate and reproducible results is required.
In electrophoresis, the initial step is to apply the sample material to the electrophoretic medium and allow the separation to take place by migration under the influence of an applied electric field. Thereafter the slide is fixed chemically, dried and subsequently read either directly or with appropriate densitometer devices. To obtain a practical migration apparatus, the device must be capable of obtaining accurate and highly reproducible results even when operated by relatively unskilled technicians. In order to provide such accuracy and reproducibility, there are a number of variables which must be precisely controlled. These include the value of the applied voltage, the time duration for migration, the voltages applied, the geometry of mounting and holding the slide during the period of migration and the temperature maintained during the period of migration.
For a large area of slide, for example, a rectangular slide approximately 9 by 6 inches, with an applied voltage of approximately 200 volts, the slide would undergo an increase in temperature to values above 55.degree.C. At these elevated temperatures, drying of the slide occurs with an increase in ionic concentration, in turn causing further power dissipation and further increase in temperature. Additionally, denaturing of proteins takes place at these high temperatures. Finally, it is desirable to maintain the slide in a constant temperature environment during electrophoresis. Variations in slide temperature during separation, while not affecting information content, do cause variations in mobility of individual protein components during electrophoresis. By performing electrophoretic separation at a constant temperature comparison of patterns between slides is facilitated.
In the past, various conventional cooling techniques have been employed. These include both water cooling a member in thermal contact with the slide and various air cooling approaches. For a slide which must necessarily have each of its ends inserted in a chemically active buffer material and have a voltage of approximately 200 volts applied across it, such cooling arrangements complicate the design of the migration apparatus and render it somewhat difficult to manipulate in routine laboratory procedures.
It is, therefore, the primary object of the present invention to provide an electrophoresis migration apparatus allowing for ease of handling, economy of operation, and precise results, while maintaining the electrophoretic slide at a substantially constant temperature between 5.degree.C and 40.degree.C.